I'd say go get some reflectix. I think the rolls are 2' by 16' for like 15 bucks where I get them. Been using a 4 foot piece of reflectix and a mummy sleeping bag for a top quilt. Slept toasty in the high 40s.
Either reflectix or ccf. The Reflectix is warmer to me but not as comfortable as a pad.
I just tested a 20 in by 6 ft piece of reflectex on a 40 degree night with wind from 35-45mph. Worked perfectly - stayed toasty warm all night.
One thing I discovered is that with pads you're going to want to anchor it so it doesn't slip around. I had to use a small binder clip on the pad and double bottom layer to keep mine from getting out of position.
If you have a single bottom layer, you may have to use more than one binder clip. Also, I have a bridge hammock so rectangular things fit it. If you have a standard shape hammock (gathered end), you may want to use/make a 3-4 ft wide piece of reflectex with the ends cut/taped at a 45 deg angle (see wanky character depiction below). That will make it more closely fit a gathered end hammock.
\_______/ <- shape of one side, tape along bottom/angle cut as needed
“I held a moment in my hand, brilliant as a star, fragile as a flower, a tiny sliver of one hour. I dripped it carelessly, Ah! I didn't know, I held opportunity.” - Hazel Lee